CODEWITHSUNDEEP
c#cachingtask
Traffy
Traffy

Reputation: 2861

Caching task results - AsyncLazy does not contain a definition for GetAwaiter

I'm trying to put a caching system in place as per a tutorial I followed. The concept seems easy to understand but when it comes to implement it, I'm getting the following error message :

'AsyncLazy' does not contain a definition for 'GetAwaiter' and the best extension method overload 'AwaitExtensions.GetAwaiter(TaskScheduler)' requires a receiver of type 'TaskScheduler'

Here below is my code : 

using System;
using System.Linq;
using System.Runtime.Caching;
using System.Threading.Tasks;
using Microsoft.VisualStudio.Threading;

public class TaskCache : ITaskCache
    {
        private MemoryCache _cache { get; } = MemoryCache.Default;
        private CacheItemPolicy _defaultPolicy { get; } = new CacheItemPolicy();

        public async Task<T> AddOrGetExisting<T>(string key, Func<Task<T>> valueFactory)
        {

            var asyncLazyValue = new AsyncLazy<T>(valueFactory);
            var existingValue = (AsyncLazy<T>)_cache.AddOrGetExisting(key, asyncLazyValue, _defaultPolicy);

            if (existingValue != null)
            {
                asyncLazyValue = existingValue;
            }

            try
            {
                var result = await asyncLazyValue; // ERROR HERE

                // The awaited Task has completed. Check that the task still is the same version
                // that the cache returns (i.e. the awaited task has not been invalidated during the await).    
                if (asyncLazyValue != _cache.AddOrGetExisting(key, new AsyncLazy<T>(valueFactory), _defaultPolicy))
                {
                    // The awaited value is no more the most recent one.
                    // Get the most recent value with a recursive call.
                    return await AddOrGetExisting(key, valueFactory);
                }
                return result;
            }
            catch (Exception)
            {
                // Task object for the given key failed with exception. Remove the task from the cache.
                _cache.Remove(key);
                // Re throw the exception to be handled by the caller.
                throw;
            }
        }
     }

I don't really get what's wrong since I declared my method as async so any lead would be appreciated.

Upvotes: 0

Views: 318

Answers (1)

Guru Stron
Guru Stron

Reputation: 143453

It seems that you need to invoke GetValueAsync on your asyncLazyValue like this var result = await asyncLazyValue.GetValueAsync();

Upvotes: 1

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